We're beginning to turn this serious health problem around. That is very good news for efforts to get our health-care costs under control.

As every governor knows, the growth in Medicaid spending is one of the major threats to states' fiscal sustainability. Medicaid currently consumes 24 percent of total states' funds. Spending on the program has grown at an annual average rate of 7.2 percent over the past decade, and that growth rate is projected by the Centers for Medicare and Medicaid Services to increase to 8.1 percent in the current decade. The cost of Medicaid now exceeds that of K-12 education as the largest area of state spending and is beginning to squeeze out other programs.

Getting Medicaid spending under control might seem to be a hopeless goal, but it isn't hopeless at all. The single most effective strategy would be to return childhood obesity rates to their historic levels, and there are encouraging developments in places as diverse as New York City and Mississippi.

That positive news couldn't be coming at a better time. As the Trust for America's Health and the Robert Wood Johnson Foundation have reported, childhood obesity rates have essentially tripled in the past 30 years, from 6.5 percent in 1980 for children ages 6 to 11 to 19.6 percent in 2008. For teens ages 12 to 18, the obesity rate climbed from 5 percent in 1980 to 17 percent in 2010.

The impact of those numbers on health-care costs is clear. Laura Segal, writing on the Trust for America's Health website, reports that being obese puts a person "at increased risk for more than 20 major diseases, including type 2 diabetes and heart disease." Alvin Powell, writing in the Harvard Gazette, notes that diabetes cases essentially have doubled in the last 20 years and that diabetes "is the nation's seventh-leading cause of death and a prime cause of kidney failure, blindness, nontraumatic limb amputations, heart disease, and stroke." Twenty-six million Americans had diabetes in 2010, and direct and indirect costs came to $174 billion, Powell reports.

Poor kids are more likely to be obese and more likely to be on Medicaid, and the incidence of type 2 diabetes among children, which used to be rare, now is on the rise. Moreover, a recent study shows that the disease progresses more rapidly in children than in adults and is harder to treat. "It's frightening how severe this metabolic disease is in children," David M. Nathan, an author of the study and director of the diabetes center at Massachusetts General Hospital, told the New York Times. "It's really got a hold on them, and it's hard to turn around."

So it's encouraging that the rate of increase in childhood obesity has leveled off in recent years and in some jurisdictions is even showing declines. Between the 2006-07 and 2010-11 school years, for example, New York City saw a 5.5 percent decline in the obesity rate among children in grades K-8. Philadelphia not only achieved an overall decline in obesity rates among K-12 students, but also reported the largest declines among African-American males and Hispanic females, two groups with disproportionately higher obesity rates.

Mississippi, which has the highest rate of obesity of any state, showed the greatest percentage decline, according to a recent report by the Robert Wood Johnson Foundation: In the spring of 2005, 43 percent of Mississippi children in grades K-5 were obese. By the spring of 2011, the rate had declined to 37.3 percent, a drop of 13.3 percent. There are likely to be many reasons for this decline, but the Healthy Students Act of 2007, which required Mississippi's public schools to provide more time for physical activity, offer healthier foods and beverages, and develop health-education programs, appears to have played a role.

Governors, mayors and other policy makers who've been looking at programs like first lady Michele Obama's Let's Move! initiative as little more than a feel-good kind of thing ought to give those programs a second look. There isn't any good reason why we couldn't bring childhood obesity back to the where it was in 1980, and doing so would be a lot more effective in reducing Medicaid and other public health-care costs than tinkering with provider rates and eligibility structures.

There are dozens of organizations and efforts focused on this issue, and real progress will probably take an "all-of-the-above" sort of strategy. Once people see the connections and the implications, getting them on board ought be as easy as child's play or as simple as a brisk, invigorating walk in the park.